1. Field of the Invention
This invention relates to subterranean slurry mining and more particularly relates to a method and apparatus for drilling and mining one or more layers of granular ore, such as phosphate or coal, without withdrawing the apparatus from the hole between the drilling and mining modes of operation.
2. Description of the Prior Art
Subterranean slurry mining of phosphates or the like is broadly known in the art as evidenced by United States Wenneborg et al. U.S. Pat. Nos. 3,730,592 and 3,747,696 which issued on May 1, 1973 and July 24, 1973, respectively, and are assigned to the assignee of the present invention. The disclosures of both of these patents are incorporated by reference herein.
The modified embodiment of the device disclosed in Wenneborg et al 3,747,696 is the most pertinent prior art embodiment and comprises a combination drilling and slurry mining apparatus which may be changed between its drilling mode of operation and its mining mode of operation to mine several different layers of ore without requiring that the apparatus be pulled out of the hole. However, both Wenneborg patents disclose apparatus having only two conduit strings for conducting processing fluids into, and the slurry out of the ore strata.
Wenneborg et al 3,730,592 discloses a method which contemplates the use of surface controlled pressures equal to or in excess of the drilling pressure for shifting the mining nozzle, the eductor nozzle, and the drilling bit valve between the drilling mode and the mining mode. In addition, the patentee discloses the use of control pressures which lie in a range between the drilling pressure and the mining pressure for modulating the mining nozzle. Modulation of the mining nozzle is effective to control the cavity pressure, and also the liquid level in the mined cavity to vary the mining conditions for the particular stratum being mined.
United States parent and divisional U.S. Pat. Nos. 3,155,177 and 3,316,985 which issued to Fly on Nov. 3, 1964 and May 2, 1967, respectively, disclose a method and apparatus for under-reaming or slurry mining a hole and can also be controlled to alternately bore deeper and mine other strata in the hole after the first boring and mining operations have been completed. Valves operated by electric motors located within the tool string convert the apparatus from a drilling operation to a mining operation. The amount of force that can be applied to convert the apparatus from the drilling operation to the mining operation is, accordingly, limited by the size of the electric motors that can fit within the tool spring.
Andrews U.S. Pat. No. 1,071,199 dated Aug. 26, 1913 discloses a drill bit mounted on the lower ends of concentric pipes with the inner pipe communicating with the material removed by the bit. During drilling, water is forced into the hole outside of the outer pipe and raises with the cuttings into the inner pipe. Compressed air is forced downwardly between the outer and inner pipes and enters the lower end of the inner pipe for pumping or lifting the cuttings upwardly to the surface.
U.S. Pat. No. 2,518,591 which issued to Ashton et al on Aug. 15, 1950 discloses a jet mining and excavating apparatus wherein jets of water are used to sink bore holes into alluvial deposits. In one embodiment a combined sinking and excavating unit is provided wherein water moves downwardly within an outer conduit and through vertical and horizontal nozzles into the hole. In another embodiment the apparatus includes a sinking unit and a separate excavating unit which is substituted for the sinking unit when the bore holes reaches the mineralized strata. The resulting slurry moves upwardly into the surface through an eccentrically disposed inner pipe. Certain embodiments of the excavating unit are oscillated through a partial or a complete circle and include a nozzle directed in a horizontal direction to reduce a large segment of the material to be excavated to a slurry. Compressed air may also be directed into the cavity formed by the jet through a pipe which is apparently external of the water pipes to pressurize the cavity permitting the horizontal jet to operate in the air rather than underwater.
Sewell U.S. Pat. No. 2,537,605 which issued on Jan. 9, 1951 discloses several embodiments of an apparatus for drilling bore holes wherein water is directed downwardly in the borehole externally of the apparatus and in mud is drawn upwardly through a central conduit. Air is directed downwardly between an outer and inner conduit to aerate the mud and raise it to the surface.
Gilmore U.S. Pat. No. 2,745,647 which issued on May 15, 1956 discloses an apparatus for making underground storage cavities and for recovery of sediments from subterranean deposits. The apparatus, however, is lowered into a previously drilled and cased hole. Water is directed through horizontal nozzles to form the cavity, and air is directed into the cavity either through the nozzles or a separate tube to provide sufficient pressure to airlift the sediment to the surface through a central tube.
U.S. Pat. No. 3,393,013 which issued to Hammer et al on July 16, 1968 discloses a process for mining ore within a well that is drilled and cased by a drill unit. A pumping unit is then lowered into the casing and has a lower end that extends out of the bottom thereof. A jet stream is provided for directing jets of water against the ore to reduce the ore in a slurry. A production line having an ore lift string therein in provided to lift the slurry to the surface. The jet stream is rotatable about the non-rotatable production line; and both the jet stream and the production line may be reciprocated vertically relative to each other.
A paper dated July 20, 1976 by Flow Research Inc., Presentation No. 102, entitled "Field Demonstration of Hydraulic Borehole Mining of Coal", discloses a subterranean mining tool which is lowered into a hole previously bored into a coal strata. The apparatus includes three eccentric pipes with the outer pipes flanged and bolted together. The apparatus is rotated during mining and includes at least one mining nozzle for reducing the coal to a slurry, and a jet pump for lifting the slurry to the surface.